Abstract

Based on the sandstone from the slope of Baorixile open-pit mining area in Hulunbuir City, Inner Mongolia, the dynamic uniaxial compression test of sandstone with different freeze-thaw cycles has been carried out by Split Hopkinson Pressure Bar test (SHPB). The test results show that the crushing degree of sandstone becomes serious with the freeze-thaw cycle times and strain rate increases. The dynamic compressive strength increases with the raise of strain rate under the same freeze-thaw cycles, while it reduces with the increases of freeze-thaw cycles at the same strain rate. It is found that the 10 freeze-thaw cycles are an obvious inflection point. When it is less than 10 cycles, the dynamic compressive strength of sandstone specimens decreases rapidly, it is more than 10 cycles, and the strength decreases gradually. This is due to that the evolution progress of pores in sandstone is more uniform after a certain number of freeze-thaw cycles. Meantime, the effect of freezing and thawing is mostly restrained by the pore evolution. On the other hand, the dissipated energy required for sandstone failure grows up with the increase of the number of freeze-thaw cycles. It shows that more energy is needed for the engender of pores and fractures in sandstone caused by freeze-thaw cycle. This led to the deterioration of sandstone structural stability and the decrease of dynamic mechanical properties.

Highlights

  • More than 70% of the land area of China is perennially frozen and seasonally frozen

  • The dynamic compressive strength of sandstone rises with the increase of strain rate. This is due to that under the impact load of high strain rate, the sandstone with the same number of freeze-thaw cycles needs more stress, which leads to the failure of sandstone samples

  • The compressive strength declines with the increase of freeze-thaw cycles

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Summary

Introduction

Some areas in the northeast and high-altitude areas in the west are permafrost regions, while north and south China are seasonal permafrost regions [1] These frozen regions are rich in mineral resources, and the rock mass will inevitably receive dynamic loads such as impact of drilling and blasting in the process of mineral mining. The study of mechanical properties and failure law of rock under the combined action of freeze-thaw and dynamic load is of great significance to rock mass engineering in frozen regions. The dynamic uniaxial compression tests of sandstone under different freeze-thaw cycles are studied in detail, and its failure mechanism is analyzed from the point of view of energy

Samples and Test Methods
Test Results
Discussion
Conclusions

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